The child was part of a clinical trial in which researchers were investigating the effect of treating HIV-positive babies in the first few weeks of life, and then stopping and starting the ART medicines while checking whether their HIV was being controlled.

The case was revealed Monday at an AIDS conference in Paris.

"It's a case that raises more questions than it necessarily answers," said Linda-Gail Bekker, president of the International AIDS Society, which is holding the conference in Paris this week.

"It does raise the interesting notion that maybe treatment isn't for life," she said, adding that "it's clearly a rare phenomenon."

Researchers believe that intensive treatment soon after infection could enable long-term remission of the disease.

Treatment with ART started when the child was almost nine weeks old but was interrupted at 40 weeks when the virus had been suppressed, and the child was monitored regularly for any signs of relapse.

The South African child, who contracted the virus from its mother, is the third who achieved a long remission using this approach.

Other similar cases include a French woman aged roughly 20 who was born with HIV and has her infection under control despite no HIV medicines since she was around six, and a Mississippi baby born with HIV in 2010 suppressed her infection for 27 months after stopping treatment before it reappeared in her blood. She was able to get the virus under control again after treatment resumed.

However, researchers believe the South African case is the first instance of sustained virological control from a randomised trial of ART interruption following early treatment of infants.

"At age 9.5 years, the child was clinically asymptomatic," the researchers said.

UNAIDS, the United Nations HIV/AIDs agency, said last week that 19.5 million people worldwide are now receiving treatment.

The vast majority of patients with HIV find that the virus increases in the body if they stop treatment, but this child was different, according to researchers.

Sharon Lewin, an HIV expert at the University of Melbourne and co-chair of the IAS's HIV Cure and Cancer forum, said the case threw up possible insights into how the human immune system can controls HIV replication when treatment is interrupted.

Yet in terms of the scientific search for a cure for HIV and AIDS, she said, it appeared only to confirm previous reports of similarly rare cases.

"We know that very rarely, people who have had treatment and stopped it are then able to control the virus."

The HIV/AIDs pandemic has killed around 35 million people worldwide since the 1980s.